Details in Military Notes Led to Shift on Iran, U.S. Says

WASHINGTON, Dec. 5 — American intelligence agencies reversed their view about the status of Iran’s nuclear weapons program after they obtained notes last summer from the deliberations of Iranian military officials involved in the weapons development program, senior intelligence and government officials said on Wednesday.

The notes included conversations and deliberations in which some of the military officials complained bitterly about what they termed a decision by their superiors in late 2003 to shut down a complex engineering effort to design nuclear weapons, including a warhead that could fit atop Iranian missiles.

The newly obtained notes contradicted public assertions by American intelligence officials that the nuclear weapons design effort was still active. But according to the intelligence and government officials, they give no hint of why Iran’s leadership decided to halt the covert effort.

Ultimately, the notes and deliberations were corroborated by other intelligence, the officials said, including intercepted conversations among Iranian officials, collected in recent months. It is not clear if those conversations involved the same officers and others whose deliberations were recounted in the notes, or if they included their superiors.

The American officials who described the highly classified operation, which led to one of the biggest reversals in the history of American nuclear intelligence, declined to describe how the notes were obtained.

But they said that the Central Intelligence Agency and other agencies had organized a “red team” to determine if the new information might have been part of an elaborate disinformation campaign mounted by Iran to derail the effort to impose sanctions against it.

In the end, American intelligence officials rejected that theory, though they were challenged to defend that conclusion in a meeting two weeks ago in the White House situation room, in which the notes and deliberations were described to the most senior members of President Bush’s national security team, including Vice President Dick Cheney.

“It was a pretty vivid exchange,” said one participant in the conversation.

The officials said they were confident that the notes confirmed the existence, up to 2003, of a weapons programs that American officials first learned about from a laptop computer, belonging to an Iranian engineer, that came into the hands of the C.I.A. in 2004.

Ever since the major findings of the new National Intelligence Estimate on Iran’s nuclear program were made public on Monday, the White House has refused to discuss details of what President Bush, in a news conference on Tuesday, termed a “great discovery” that led to the reversal.

Some of Mr. Bush’s critics have questioned why he did not adjust his rhetoric about Iran after the intelligence agencies began to question their earlier findings.

In a statement late Wednesday, the White House revised its account of what Mr. Bush was told in August and acknowledged that Mike McConnell, the director of national intelligence, had informed him new information might show that “Iran does in fact have a covert weapons program, but it may be suspended.”

Dana Perino, the White House press secretary, said Mr. McConnell had warned the president that “the new information might cause the intelligence community to change its assessment of Iran’s covert nuclear program, but the intelligence community was not prepared to draw any conclusions at that point in time, and it wouldn’t be right to speculate until they had time to examine and analyze the new data.”

A senior intelligence official and a senior White House official said that Mr. McConnell had been cautious in his presentation to Mr. Bush in an attempt to avoid a mistake made in the months leading to the Iraq war, in which raw intelligence was shared with the White House before it had been tested and analyzed.

“There was a big lesson learned in 2002,” the senior intelligence official said. “You can make enough mistakes in this business even if you don’t rush things.”

In fact, some in the intelligence agencies appear to be not fully convinced that the notes of the deliberations indicated that all aspects of the weapons program had been shut down.

The crucial judgments released on Monday said that while “we judge with high confidence that the halt lasted at least several years,” it also included the warning that “intelligence gaps discussed elsewhere in this Estimate” led both the Department of Energy and the National Intelligence Council “to assess with only moderate confidence that the halt to those activities represents a halt to Iran’s entire nuclear weapons program.”

The account is the most detailed explanation provided by American officials about how they came to contradict an assertion, spelled out in a 2005 National Intelligence Estimate and repeated by Mr. Bush, that Iran had an active weapons program.

Several news organizations have reported that the reversal was prompted in part by intercepts of conversations involving Iranian officials. In an article published on Wednesday, The Los Angeles Times said another main ingredient in the reversal was what it called a journal from an Iranian source that documented decisions to shut down the nuclear program.

The senior intelligence and government officials said a more precise description of that intelligence would be exchanges among members of a large group, one responsible for both designing weapons and integrating them into delivery vehicles.

The discovery led officials to revisit intelligence mined in 2004 and 2005 from the laptop obtained from the Iranian engineer. The documents on that laptop described two programs, termed L-101 and L-102 by the Iranians, describing designs and computer simulations that appeared to be related to weapons work.

Information from the laptop became one of the chief pieces of evidence cited in the 2005 intelligence estimate that concluded, “Iran currently is determined to develop nuclear weapons.”

The newly obtained notes of the deliberations did not precisely match up with the programs described in the laptop, according to officials who have examined both sets of data, but they said they were closely related.

On Wednesday President Bush repeated his demand that Iran “come clean” and disclose details of the covert weapons program that American intelligence agencies said operated from the 1980s until the fall of 2003.

Iran’s government, Mr. Bush said, “has more to explain about its nuclear intentions and past actions, especially the covert nuclear weapons program pursued until the fall of 2003, which the Iranian regime has yet to acknowledge.”

Mr. Bush spoke at Eppley Airfield near Omaha, where a visit intended to showcase health care and to raise money for a Senate race was overshadowed by the furor caused by the National Intelligence Estimate and Iran’s taunting reaction to it.

He faced calls from across the political spectrum for the United States to make a more concerted effort to negotiate with Iran, offering a package of incentives that could persuade it to suspend its uranium enrichment program and clear up concerns that it is building a civilian energy program to develop the expertise for a covert military program.

“Bush has made a big mistake, and he’s not responding in a way that gives confidence that he’s on top of this,” said David Albright, a former weapons inspector for the International Atomic Energy Agency and president of the Institute for Science and International Security. “He isn’t able to respond because he’s not able to say he’s wrong.”

Mr. Bush, though, made it clear that there would be no immediate change in the United States’ approach, saying that the administration had already offered to talk, though on the condition that Iran suspend its current enrichment program first, as called for in two United Nations Security Council resolutions. Administration officials have said that they would continue to advocate tougher sanctions, which seems increasingly unlikely.

A version of this article appears in print on , on page A1 of the New York edition with the headline: U.S. SAYS DETAILS INMilitaryNotes Led to Iran Shift. Order Reprints|Today's Paper|Subscribe